Fine temperature controllable wafer heating system

ABSTRACT

Disclosed are a method and a system for processing wafers in fabricating a semiconductor device where disposing chemicals and wafer heating are needed for chemical reaction. A wafer is placed above a wafer heater such that a second surface faces the wafer heater, and heated from the second surface. A chemical layer is formed on an opposing first surface. The wafer heater is sized and configured to be capable of heating the entire second surface, and adapted to produce a locally differential temperature profile if needed. During heating, an actual temperature profile on the wafer may be monitored and transmitted to a computing system, which may generate a target temperature profile and control the wafer heater to adjust local temperatures on the wafer according to the target temperature profile. A supplemental heater for heating the chemicals may be used for finer control of the wafer temperature.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/786,290, filed on Mar. 14, 2013.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. In addition to IC componentsbecoming smaller and more complex, wafers on which the ICs arefabricated are becoming larger. For example, current wafer size is 300mm, and in coming 5 year may enter into 450 mm wafer production.

Wafers are processed in many ways, some of which are done while thewafer is secured on a planar wafer platform (e.g., table, holder, orchuck) in a process chamber of a wafer processing tool. In many steps ofwafer processing, such as pre-cleaning, post-cleaning, or variousetching steps, chemical materials such as cleaning agents or etchantsare added to a surface of the wafer to form or modify layer(s) ofmaterial on the surface. To boost chemical reactions for the process,the wafer often needs to be heated to a suitable temperature. In theconventional methods practiced in the current art, the heat is directlysupplied to the layer formed on the wafer by an overhead heater locatedabove the wafer, and thereby, to the wafer below. Some heaters areconfigured to move over the wafer surface, and some are fixed.

The current methods practiced in the art, however, have a severaldeficiencies. One is caused by a non-uniform heat distribution acrossthe wafer. Since the overhead heater heats the chemical layer onlylocally, the layer and the wafer below cannot have uniformity intemperature. Even if the heater is configured to move around over thewafer while heating, the uniformity obtainable is limited and thenon-uniformity cannot be totally eliminated. The non-uniformity intemperature is aggravated by the increased wafer size, as well as anynon-uniformity in the chemical layer itself caused by the currently usedsystem of depositing chemical material on the wafer, which typicallyuses sprayers. With such sprayers, whether moving or fixed, the materialsprayed on the wafer will not be uniform.

Another deficiency is due to directly heating up the chemical materials.The temperature to which the chemical materials are heated is subject toa temperature constraint imposed by the chemical property of thechemical materials. For example, the chemical material may need to beheated up past its boiling point for various reasons, at which thematerial changes from liquid to gas. Since the temperature of thechemicals does not change for the duration of the phase change of thechemicals despite continued application of heat energy, the temperatureof the wafer does not increase as desired at the cost of heat energyduring this period. Moreover, the abrupt, dramatic volume expansion ofthe chemical gas following the liquid-gas phase change not only impairsthe reaction rate from the loss of available liquid state chemicals atwhich most chemical reactions most actively occur, but also causespattern damage or collapse. Further, in the high temperature environmentin the vaporized phase of the chemicals in which the temperature rapidlyincreases, it is much harder to control or fine-tune a temperatureprofile on the wafer as precisely as desired for optimum reaction rateand uniformity.

Therefore, to prevent the pattern collapse induced by sudden volumeexpansion of vaporized chemical gas, to ensure more fine-tuned controlover the temperature of the wafer and thus over optimum reaction rate,and to obtain more temperature uniformity across the wafer, it isdesirable to provide a method and a system for heating up a wafer thatcan produce a uniform, or any desired temperature profile on the waferdetermined for optimum reaction rate. Further, it is also desirable toprovide a method and a system for heating up a wafer that can provide acloser and finer control over the temperature of the wafer in a mildertemperature environment that does not invoke the damaging expansion ofthe chemical gas on the wafer surface from its phase change.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with accompanying figures. It is emphasized that,in accordance with the standard practice in the industry, variousfeatures in the drawings are not drawn to scale and are used forillustration purpose only. In fact, the dimension of the variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 schematically shows a system and a method performed to processwafers, particularly for heating a wafer, in fabricating a semiconductordevice in an aspect of the present disclosure;

FIG. 2 is a typical phase change diagram for a chemical materialdisposed on a wafer during a wafer processing for fabricating asemiconductor device;

FIG. 3 is a schematic diagram of a method performed to process wafers infabricating a semiconductor device in an aspect of the presentdisclosure;

FIGS. 4A-4C schematically show examples of a wafer heater used in thesystem and method performed to process wafers in fabricating asemiconductor device according to aspects of the present disclosure;

FIG. 5 is a schematic view of part of the system and method performed toprocess wafers in fabricating a semiconductor device, particularly forheating a wafer, in an aspect of the present disclosure; and

FIG. 6 a schematic diagram of a step in the method performed to processwafers, particularly for heating a wafer, in fabricating a semiconductordevice in an aspect of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the disclosure.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. For example, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

The present disclosure is directed to a method and system of heating awafer during a wafer processing for fabricating a semiconductor device.More particularly, the present disclosure provides a way to heat up awafer in more controlled, fine-tuned way in a milder temperatureenvironment so that the problem of potential pattern collapse fromexplosive expansion of chemical gas from its liquid-gas phase transitionat high temperature may be prevented. Further, the method and system inthe present disclosure enables the wafer to be heated up in any desiredtemperature profile, whether uniform or spatially differential, throughdirect heating of the wafer so as to boost up the chemical reaction rateon the wafer, and thereby speeds up the wafer processing.

FIG. 1 describes a system 100 for implementing various embodiments ofthe present disclosure. The system includes a wafer processing platform130 in a process chamber, upon which a wafer 110 is to be placed forvarious kinds of wafer processing. The platform 130 could be a flatstage, such as a wafer stage in a stepper, sized and configured to placethe wafer 110 of various sizes used in the current art thereon forprocessing. The platform 130 may have a suitable means for securing thewafer 110 so that the wafer 110 may not be displaced, shaken, ormisaligned during the processing. In some embodiment, the platform maybe equipped with a suitable means for make an ultra-fine alignment ofthe wafer 110 to a predetermined orientation and position for a highlyprecise processing. This system will be further discussed below, withreference to the method of FIG. 3.

FIG. 2 is a typical phase change diagram for a chemical material. Duringthe time intervals of two phase changes, from solid to liquid and fromliquid to gas, respectively, the temperature curve forms plateaus, atwhich the temperature stays stationary despite continued application ofheat energy. Such a nonlinear, deadlock situation in the behavior of thetemperature of the chemical material during the phase change makes ithard to control the temperature of the wafer. A greater problem for theconventional way of directly heating the chemical material is that theinevitable liquid to gas phase change results in abrupt and dramaticexpansion of the volume of the chemical gas, which in turn may induceserious deformation or collapse of the pattern formed on the wafer.

FIG. 3 is a schematic diagram of a method 300 performed to processwafers in fabricating a semiconductor device in an aspect of the presentdisclosure. The steps of the method 300 in FIG. 3 will be describedherein while referring to FIGS. 1, 4A-C, 5, and 6, which schematicallyshow selected steps of the method 300.

Referring to FIG. 3, at step 302, a wafer heater is provided. Herein,the word ‘provide’ is used in a broad sense to encompass all modes ofprocurement, including, but not limited to, ‘purchasing’, ‘preparing’,‘manufacturing’, ‘arranging’, ‘setting in order’, or ‘bringing in foruse’ the object of provision, which is, in the instant case, the waferprocessing platform. Referring also to FIG. 1, a first wafer heater 120is disposed, in an embodiment of the present disclosure, upon a waferprocessing platform 130 in a process chamber. For some embodiments, asecond heater 122 is disposed above the platform 130, and above wherethe wafer 110 will be positioned in the process chamber. In someembodiment, the platform 130 may be equipped with a suitable means formake an ultra-fine alignment of the wafer 110 to a predeterminedorientation and position for a highly precise processing. Also, in oneembodiment, the platform 130 may further equipped with a suitable meansfor rotating the wafer 110 during a chemical layer formation, heatingthe wafer, or other wafer processing steps. Such means for securing,aligning, or rotating the wafer 110 is well known in the art and notdescribed herein further in detail.

Like the platform 130, the first wafer heater 120 is accordingly sizedand configured to cover an entire surface of a wafer, and heat itsubstantially uniformly and simultaneously. The wafer 110 to be heatedin the method 300 of the present disclosure may be any typical a thinsliced wafer used in the art, which is made of a suitable semiconductormaterial, such as a silicon crystal, and serves as a substrate forvarious microelectronic devices to be built in and over the waferthrough many, in some cases more than 400, micro-fabrication processsteps, such as doping or ion implantation, etching, deposition ofvarious materials, and photolithographic patterning. The wafer 110 maybe of any standard size, including the commonly used 400 mm and 450 mmwafers with respective thicknesses. As the size of the wafer 110changes, the size of the first wafer heater 120 changes accordingly.Further, since the typical configuration of a standard wafer is a thindisc, the first wafer heater 120 may have a circular configuration aswell in an embodiment.

In one embodiment, the first wafer heater 120 may be rigidly attached tothe upper surface of the platform 130 and configured to rotate togetherwith the wafer 110 placed upon the upper surface of the wafer heater 120if the particular embodiment demands rotating the wafer 110 during thechemical material application and/or heating and/or other waferprocessing. In this case, the upper surface of the first wafer heater120 should be flat and suitably configured to securely hold the wafer110 thereon. In another embodiment, the first wafer heater 120 may beslightly separated from the platform 130 while still being disposedabove it. Further, in still another embodiment, the wafer 110 may not beplaced directly upon the physical surface of the first wafer heater 120,but slightly separated therefrom while the lower surface of the wafer110 is facing parallelly the surface of the first wafer heater 120 asshown in FIG. 1. In this particular embodiment, the separation betweenthe wafer 110 and the heater 120 is suitably determined such that stillan effective heating may be performed despite the separation. In thiscase, there may be a separate means for securing, aligning, or rotatingthe wafer 110 during the heating, chemical layer forming, or otherprocessing in one embodiment, or in another, they may be the same onesthat are equipped to the platform 130 mentioned above.

In an embodiment of the present disclosure, the first wafer heater 120is adapted to heat up the wafer 110 to produce any differentialtemperature profile as desired or targeted. Depending on a particulartype of a wafer processing step, the wafer 110 may sometimes need to beheated up uniformly so that it may have the same temperature across itsentire area. At other times, the wafer 110 may need to be heated updifferentially such that different areas on it may have differenttemperatures according to some predetermined temperature profile.Accordingly, in the referred particular embodiment, the first waferheater 120 is configured to be capable of heating any particular portionof a wafer 110 that is facing the heater 120, either in contacttherewith or slightly separated therefrom, up to any particular presettemperature. For that, the first wafer heater 120 may have a variety ofdifferent structures and modes that serve the purpose.

In one embodiment, schematically illustrated in FIG. 4A, the first waferheater 120 may have a plurality of radiation sources or lamps 422 asheat sources, which are attached to one face of a base, made of aceramic or other suitable material. Each radiation source 422 iselectrically coupled to a temperature control unit (not shown) such thatthe power supplied thereto or the heat energy radiated therefrom may beindividually controlled. By controlling the power or heat energy ofindividual radiation sources 422, the first wafer heater 120 cangenerate any differential temperature profile as desired and heat up thewafer 110 accordingly.

In another embodiment, now schematically illustrated in FIG. 4B, thefirst wafer heater 120 may have a plurality of heat coils 424 as heatsources that are concentrically arranged and attached to one face of abase, again made of a ceramic or other suitable material. Again, thecoils 424 may be electrically coupled to a temperature control unit (notshown) such that the power supplied to, or the heat energy radiatedfrom, coils of different diameters, or portions in a single coil of asame radius but different circumferential positions, may be individuallycontrolled. Then, the wafer 110 can be heated up with differenttemperatures at different locales according to any predetermineddifferential temperature profile by controlling the power or heat energyof individual coils 424.

In still another embodiment, the first wafer heater 120 may have aplurality of heating plates or panels 426 formed on one face of a basemade of a ceramic or other suitable material as schematically shown inFIG. 4C. The heating plates 426 may have an annular configuration and becircumferentially arranged as shown in FIG. 4C in an embodiment, but inother embodiments, they may have, and be arranged in, any other suitablegeometrical configuration, for example, square or rectangular heatingplates arranged in a meshed or laddered fashion. The number, theindividual size or configuration of the heating plates 426 also may besuitably adjusted according to different design needs. Whatever thenumber, size, configuration, or arrangement of the individual heatingplates 426 is, the heating plates 426 may be electrically coupled to atemperature control unit (not shown) such that the hear energy producedfrom a particular heating plate 426 at a particular position may beindividually controlled, just as in other embodiments described above.Then, the wafer 110 can be heated up, again, to any temperature profiledesired by controlling the power supplied to each individual heatingplate 424 of the first wafer heater 120.

Referring back to FIG. 3, at step 304, a wafer is placed over the waferheater. FIG. 1 schematically shows how the wafer 110 is disposed withrespect to the first wafer heater 120 in an embodiment of the presentdisclosure. The wafer 110 used herein is any typical thin sliced waferused in the current art, made of a suitable semiconductor material, suchas a silicon crystal, and serving as a substrate for variousmicroelectronic devices that are to be built in and over the waferthrough hundreds of micro-fabrication process steps. The wafer 110 hastwo opposing surfaces, a first wafer surface 102 and a second wafersurface 104, and placed over the first wafer heater 120 such that thesecond wafer surface 104 faces the first heater 120 in a parallel manneras shown in FIG. 1. The first wafer heater 120 is appropriately sizedand configured such that it is capable of applying heat to the entiresecond wafer surface 104 uniformly and simultaneously if a uniformtemperature profile is desired. In one embodiment, the wafer 110 may beplaced upon the first wafer heater 120, directly in contact therewith asshown in FIG. 5. If it is needed to rotate the wafer 110 during theheating process for more uniform and evener heat distribution (as shownby the arrow in FIG. 1), the wafer 110 may be configured to rotate,together with the first wafer heater 120 in an embodiment, or alone uponthe fixed heater 120 by a separate suitable rotation mechanism (notshown).

In still another embodiment, the wafer 110 may be placed over the waferheater 120, slightly separated therefrom as shown in FIG. 1. Thisembodiment may work well in a situation where the wafer 110 needs to berotated independently from the first wafer heater 120 via a separaterotation means during the process of heating or the chemical materialapplication that is to be described in the subsequent step. In thiscase, the separation between the first wafer heater 120 and the wafer110 needs to be sufficiently close so as not to impair the efficiency ofthe heating. Also, in this particular embodiment, the wafer 110 may beheld above the first wafer heater 120 by a separate securement means(not shown). Further, there may be a separate alignment means as wellfor fine alignment of the wafer 110.

Referring back to FIG. 3, now at step 306, a chemical material isdisposed over the first wafer surface 102 to form a chemical layer 140.The chemical material(s) could be any chemical(s) applied to a waferduring a wafer processing in which a chemical reaction between thechemical(s) and the wafer is desired and the wafer is heated to boost upthe chemical reaction. In one embodiment, such a wafer processing may bea pre-cleaning, a post-cleaning, or an etching process, in which case,the chemical materials may be appropriate cleaning agents or etchants.The chemical material(s) may comprise a single or multiple chemicalsmixed depending on the type of the chemical reaction needed. In oneembodiment, the chemical material(s) is in a liquid form and is sprayedupon the wafer 110 by an overhead sprayer 145 to form a thin chemicallayer 140. The wafer 110 may be rotated during the chemical layerformation for even, uniform thickness. While spraying the chemicalmaterial(s) 140, if a further uniformity is desired, the overheadsprayer 145 may move around over the wafer 110 at a regular speed tocover the entire first wafer surface 102. Some wafer processing,however, may require a formation of the chemical layer 140 of locallyvariant thicknesses. For that, the sprayer 145 may be configured tospray different amount of chemical material(s) at different locationsabove the wafer 110 via a connection to a computer control unit. FIG. 5schematically illustrates the chemical layer 140 formed upon the firstwafer surface 102 of the wafer 110. In the particular embodimentillustrated, the wafer 110 is placed such that the second wafer surface104 is directly in contact with the upper surface of the first waferheater 120. But as described hereinbefore, the wafer 110 may be placedat a small distance above the first wafer heater 120 in anotherembodiment.

Lastly, at step 308, the wafer 110 is heated by the first wafer heater120 to produce a target temperature profile on the wafer 110. As can beseen from FIGS. 1 and 5, in the present disclosure, the wafer 110 isdirectly heated by the heater 120 from the second wafer surface 104. Theheat flux flows from a wafer surface opposite to the surface where thechemical layer is formed to the very surface where it is formed. In thatarrangement, the chemical material(s) is only indirectly heated upthrough the heating of the wafer 110. The benefits of such a directheating of the wafer are obvious as compared to the conventional mannerin the current art of heating the wafer through a direct heating of thechemical material(s). The method in the present disclosure makes it mucheasier to fine-control the temperature of the wafer due to the directheating of the wafer. As will be described below, the capability offine-controlling the heating of the wafer further enables heating up thewafer according to any differential temperature profile on the wafer byclosely monitoring the temperature profile on the wafer during theheating process and readily adjusting the local power of the waferheater by an instant feedback system. Further, the problem of abrupt andradical expansion of the chemical gas as it goes through the liquid-gasphase change, which is caused by direct heating of the chemicals anddamages the patterns formed on the wafer, can be avoided. Still further,the chemical reaction rates can be boosted in the present method byheating up the wafer to a temperature even higher than the boilingtemperature of the chemical material(s) while still restraining thechemical(s) from undergoing a rapid phase change.

The target temperature profile to be achieved on the wafer 110 isdetermined, based on various process needs of a particular type of thewafer processing to be performed. In one process, a uniform temperatureprofile may be preferred. In another, a locally differential temperatureprofile may be desired. In one embodiment, the target temperatureprofile may be predetermined before the heating of the wafer 110 isstarted. In another embodiment, the target temperature profile may beobtained while being constantly adjusted during the heating process sothat the wafer 110 may have an optimum temperature profile that thatwould produce the highest chemical reaction rates or best performance inother types of wafer processing.

FIG. 6 schematically illustrates how an optimum temperature profile canbe determined in an embodiment. In the particular embodimentillustrated, a temperature sensor 610 is disposed above or adjacent thechemical layer 630 or the wafer 600 heated by the first wafer heater620. The temperature sensor 610 may constantly monitor the actual localtemperature profile on the surface of the wafer 600 and transmit theprofile to a computing system 640. On the other hand, another computingsystem 650, electrically coupled with the computing system 640, mayindependently receive real time in-line data on the various states ofthe wafer 600 and the wafer processing being performed, such as thelocal thicknesses of the chemical layer 630 being formed, the currentrate of chemical reaction occurring on the wafer 600, the progress levelof a particular wafer processing being performed, . . . etc. Based onthe actual local temperature profile and the real time in-line data, thecomputing system 650 may determine the instantaneous target temperatureprofile to be achieved and relays it to a temperature control unit,which may be present as a separate computer or a part of the computingsystem 650. According to the instantaneous target temperature profilereceived, the temperature control unit can adjust the power outputs forthe various types of individual heating elements in the first waferheater 620, illustrated in FIGS. 4A, 4B, and 4C, to control the localtemperatures on the wafer 600. Accordingly, the method 300 in thepresent disclosure may further comprise the steps of monitoring actualtemperature profile on the wafer by a temperature sensor and controllingthe target temperature profile depending on the actual temperatureprofile.

In one embodiment of the present disclosure, the method 300 may furthercomprise heating the chemical layer 140 formed on the wafer 110 by asecond heater 122 disposed above the chemical layer 140, as shown inFIG. 1, for supplemental control of the wafer temperature. Thesupplementary heater 122 may take various forms used in the current art,illustrated in FIGS. 4A, 4B, and 4C. For instance, the supplementaryheater may be a fixed one covering the entire chemical layer in anembodiment. In another embodiment, it may be positioned at a side of thechemical layer formed on a rotating wafer. In another embodiment, asteamed heating system may be employed as the supplemental heater. Thesupplementary heater used in the present disclosure is different fromthose used in the conventional heating system in the usage and function.In the conventional methods, the heater disposed over the chemical layerare the primary, in fact the only, heater used for heating up the wafer.Therefore, frequently it is needed to heat up the chemical materialseven past the boiling temperature of the chemical(s) to raise the wafertemperature to a degree sufficient for a desired chemical reaction rate,which involves many problems noted above, arising from the phase changeof the chemical(s). By contrast, the heater of the various types used inthe method of the present disclosure heats up the chemical material(s)only for a supplemental purpose, i.e., for ultra-finer control of thewafer temperature in combination with the wafer heater located under thewafer, which performs the primary heating. As such, the supplementaryheater in the present disclosure never needs to heat up the chemical(s)above the boiling temperature to cause pattern collapse problemdescribed above.

The novel method in the present disclosure of directly heating the waferduring the various wafer processing steps in fabricating a semiconductordevice provides many benefits over the conventional methods used in thecurrent art of directly heating the chemical material(s), and thereby,heating the wafer indirectly. The method in the present disclosure makesit much easier to fine-control the temperature of the wafer since thewafer is directly heated. If desired, heating up the wafer in a moreuniform temperature distribution is enabled. Further, the capability offine-controlling the heating of the wafer further enables heating up thewafer according to any differential temperature profile on the wafer asdesired. The actual temperature profile on the wafer during the heatingprocess can be monitored, and using a computing system, currenttemperature profile can be readily adjusted to a new target temperatureprofile, which can be immediately implemented on the wafer by a waferheater that is capable of heating up the wafer locally differentially asdesired. Further, the problem, commonly present in the conventionalmethod of directly heating the chemicals, of abrupt and radicalexpansion of the chemical gas in short time as it goes through theliquid-gas phase change, which seriously damages the patterns formed onthe wafer, can be avoided in the present method. Still further, sincethe temperature restraint from chemical property is removed, a higherchemical reaction rate can be obtained in the present method by heatingup the wafer even to a temperature higher than the boiling temperatureof the chemical material(s) while still restraining the chemical(s) fromundergoing a rapid phase change.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of processing wafers in fabricating asemiconductor device, the method comprising: providing a first heateradapted to heat a wafer to produce a locally differential targettemperature profile thereon; placing a wafer having opposing first andsecond wafer surfaces over the first heater such that the second wafersurface faces the first heater; disposing a chemical material over thefirst wafer surface to form a chemical layer thereon; and heating thewafer from the second wafer surface by the first heater to produce atarget temperature profile on the wafer, and wherein the wafer is heatedup to a temperature above the boiling temperature of the chemicalmaterial, and wherein the chemical layer is heated up to a temperaturebelow the boiling temperature of the chemical material.
 2. The method ofclaim 1, further comprising monitoring an actual temperature profile onthe wafer by a temperature sensor and controlling the target temperatureprofile depending on the actual temperature profile.
 3. The method ofclaim 1, wherein the first heater is sized and configured to be capableof heating the entire second wafer surface substantially uniformly andsimultaneously.
 4. The method of claim 1, further comprising heating thechemical layer by a second heater disposed over the chemical layer. 5.The method of claim 1, further comprising rotating the wafer while thewafer is heated.
 6. The method of claim 1, wherein the first heaterproduces heat from radiation sources.
 7. The method of claim 1, whereinthe first heater produces heat from electric coils attached thereto. 8.The method of claim 1, wherein the first heater produces heat from aplurality of heating plates that are capable of a differential heating.9. A method of heating wafers in fabricating a semiconductor device, themethod comprising: disposing a wafer having opposing first and secondwafer surfaces over a first heater such that the second wafer surfacefaces the first heater; forming a layer of a chemical material upon thefirst wafer surface; heating the wafer by the first heater whilecontrolling the temperature profile on the wafer so as to achieve anoptimum temperature profile thereon; and heating the layer of thechemical material by a second heater disposed above the chemical layer;wherein the wafer is heated up to a temperature above the boilingtemperature of the chemical material and the layer of the chemicalmaterial is heated up to a temperature below the boiling temperature ofthe chemical material.
 10. The method of claim 9, further comprisingrotating the first heater at a first rate of rotation while heating thewafer by the first heater.
 11. The method of claim 9, further comprisingrotating the wafer at a second rate of rotation while heating the waferby the first heater, wherein the second rate of rotation is differentthan the first rate of rotation.
 12. The method of claim 9, whereinheating the wafer by the first heater while controlling the temperatureprofile on the wafer so as to achieve the optimum temperature profilethereon includes heating a first portion of the second surface of thewafer at a first temperature by the first heater and heating a secondportion of the second surface of the wafer at a second temperature bythe first heater, wherein the first temperature is different than thesecond temperature.
 13. The method of claim 9, further comprisingmonitoring an actual temperature of the second surface of the waferduring the heating of the wafer by the first heater; and adjusting theheating of the wafer by the first heater based on the actualtemperature.
 14. A method comprising: forming a material layer over afirst side of a substrate; and heating the substrate up to a temperatureabove the boiling temperature of the material layer by applying heatfrom a first heater to a second side of the substrate and heating thematerial layer up to a temperature below the boiling temperature of thematerial layer by applying heat from the first heater to the second sideof the substrate, the second side of the substrate being opposite thefirst side and the first heater faces the second side of the substrate.15. The method of claim 14, further comprising monitoring an actualtemperature of the second side of the substrate during the heating ofthe substrate up to the temperature above the boiling temperature of thematerial layer and during heating of the material layer 1 up to thetemperature below the boiling temperature of the material layer; andadjusting the heating of the substrate by the first heater based on theactual temperature.
 16. The method of claim 14, wherein heating thematerial layer up to the temperature below the boiling temperature ofthe material layer by applying heat from the first heater to the secondside of the substrate includes applying heat from a second heater to thefirst side of the substrate.
 17. The method of claim 14, furthercomprising: rotating the first heater at a first rate of rotation whileheating the substrate up to the temperature above the boilingtemperature of the material layer by applying heat from the first heaterto the second side of the substrate and heating the material layer up tothe temperature below the boiling temperature of the material layer byapplying heat from the first heater to the second side of the substrate;and rotating the substrate at a second rate of rotation while heatingthe substrate up to the temperature above the boiling temperature of thematerial layer by applying heat from the first heater to the second sideof the substrate and heating the material layer up to the temperaturebelow the boiling temperature of the material layer by applying heatfrom the first heater to the second side of the substrate, wherein thesecond rate of rotation is different than the first rate of rotation.18. The method of claim 14, wherein heating the substrate up to thetemperature above the boiling temperature of the material layer andheating the material layer up to the temperature below the boilingtemperature of the material layer by applying heat from the first heaterto the second side of the substrate includes heating a first portion ofthe second side of the substrate at a first temperature by the firstheater and heating a second portion of the second side of the substrateat a second temperature by the first heater, wherein the firsttemperature is different than the second temperature.
 19. The method ofclaim 14, wherein the first heater covers the entire second side of thesubstrate.
 20. The method of claim 19, wherein heating the materiallayer up to the temperature below the boiling temperature of thematerial layer by applying heat from the first heater to the second sideof the substrate includes applying heat from a second heater to thefirst side of the substrate, and wherein second heater does not coverthe entire first side of the substrate.